In wire electric discharge machining, insulating machining-fluid is introduced between a wire electrode and a workpiece as electrodes, and while the wire electrode and the workpiece are moved relative to one another, machining electric power is supplied to the inter-electrode gap, and the workpiece is machined by electric discharge energy.
In this type of wire electric discharge machine that performs wire electric discharge machining, the wire electrode is fed from a supply reel at a fixed speed, is positioned above or below the workpiece, and is supplied between machining heads provided with a wire guide. Further, the machining-fluid is ejected from a nozzle disposed above or below the workpiece, whereby removal of machining waste from the inter-electrode gap, cooling, etc., are performed. To increase machining speed, it is necessary to efficiently eject the machining-fluid at high pressure into the inter-electrode gap.
For this type of goal, in machining-fluid ejection devices in conventional wire electric discharge machines, a method is generally adopted whereby the internal diameter of the nozzle that ejects the machining-fluid (hereinafter referred to as the “nozzle diameter”) and the ejection pressure of the machining-fluid are optimized.
Furthermore, in order to efficiently eject the machining-fluid into the inter-electrode gap and to suppress the influence of the pressing force of the nozzle on the workpiece, fine adjustment is necessary to have the nozzle and the workpiece as close as possible, or, where the nozzle and the workpiece are in contact (hereinafter referred to as “nozzle contact machining”), to make the pressing force of the nozzle small.
These types of problems are addressed by machining-fluid ejection devices for wire electric discharge machine apparatuses disclosed, for example, by Japanese Patent Laid-Open No. 1990-292127 (Japanese Patent No. 2656129, U.S. Pat. No. 5,128,505).
FIG. 9 is a sectional diagram illustrating a configuration for the machining-fluid ejection device in the conventional wire electric discharge machine apparatus disclosed in the above publications. In the figure, reference numeral 1 is a casing that is fixed to a machining head of the electric discharge machine, reference numeral 2 is a movable element that can slide relative to the casing 1, reference numeral 3 is a nozzle that can slide relative to the movable element 2, reference numeral 4 is a nozzle through which a wire runs, reference numeral 5 is a wire guide, reference numeral 6 is a channel, reference numeral 7 is an ejection chamber, reference numeral 8 is a pressure chamber, reference numeral 9 is a second chamber, reference numerals 10 and 11 are orifices, reference W is a workpiece. Machining-fluid from the channel 6 is supplied as a pressurized fluid flow, and the machining-fluid is ejected from the nozzle 3 towards the inter-electrode gap between the wire electrode, which is not illustrated in the figure, and the workpiece W. The pressurized chamber 8 and the second chamber 9 are configured so that the pressure of the pressurized chamber 8 and the pressure of the ejection chamber 7 act on the nozzle 3 in opposite directions, and even when the machining-fluid is ejected at high pressure into the inter-electrode gap, the influence of the reaction force on the machining head is sufficiently eased, and this arrangement enables high-accuracy, high-speed machining to be performed.
In this type of configuration for the machining-fluid ejection devices in the wire electric discharge machines, the position of the machining-fluid emitting nozzle 3 can be automatically fine-tuned relative to the workpiece W, and contact machining can be performed; however, there have been problems in that the pressurized chamber 8 and the like have to be provided, and the structure becomes complicated.
FIG. 10 is an explanatory diagram illustrating an example of machining where a distance is required between the nozzle and the workpiece (hereinafter referred to as “nozzle separation machining”). In the figure, reference numerals 12a and 12b are machining heads, reference numerals 13a and 13b are machining-fluid ejection devices, reference numeral 14 is a clamp jig for fixing the workpiece W, reference E is a wire electrode. FIG. 10(a) illustrates a case where it is necessary to perform nozzle separation machining because the clamp jig 14 that fixes the workpiece W may interfere with the upper machining-fluid ejection device member 13a, and FIG. 10(b) illustrates a case where it is necessary to perform nozzle separation machining for counter boring or rear-side residue clearing in the workpiece.
In cases where nozzle separation machining is performed, as in FIG. 10, in order to efficiently eject the machining-fluid at high pressure into the inter-electrode gap between the wire electrode and the workpiece and thus raise machining productivity, it is necessary to configure the nozzle diameter differently to the nozzle diameter when performing contact machining.
In the machining-fluid ejection device of the conventional wire electric discharge machining apparatus as in FIG. 9, in cases where the nozzle diameter is configured to be suitable for nozzle contact machining, since the nozzle diameter cannot be configured to be suitable for nozzle separation machining, there have been problems in that the machining speed decreases when performing the nozzle separation machining, and the productivity of the overall machining diminishes.